Prior art conformal blanket sonar arrays include arrangements having three distinctly different flat uniform layers adhered to one another in sandwich fashion. The three layers comprise a sound isolation baffle adhered to an exterior hull surface, a reaction plate adhered to the sound isolation baffle and a layer embedding sonar components adhered to the reaction plate. The reason for interjecting the reaction plate into this configuration involves the incompatibility between the relatively low acoustic impedance exhibited by a sound isolation baffle and the relatively high impedance environment required by acoustic sensors. The reaction plate being of sufficient mass and stiffness tends to solve this problem by permitting substantially different impedance environments to exist on either side of itself.
A requirement of conformal blanket sonar arrays is that they be made sufficiently thin and lightweight so as to permit installation over a vessel's exterior hull surface without seriously affecting the vessel's handling, stability, speed, endurance, etc. However, the tendency is to propose additions to such arrays, such as the addition of the aforementioned baffle and plate, with the objective of improving sonar performance but with an undesirable increase in thickness and weight thus hindering the vessel's sea performance and thereby partially negating one of the most desirable features of such arrays.
The packing efficiency of each layer must be considered. The layer embedding sonar components in some arrays exhibit a low packing density particularly along dimensions where self-noise is correlated over relatively large distances. Conversely, it is expected that a sound isolation layer of uniform thickness and a flat reaction plate will contain little or no unused volume.
Another drawback of the prior art involves the flexibility inherent in a flat plate. The flat reaction plate tends to lack stiffness and therefore is limited in its ability to spread the effect of its mass over relatively large areas.